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In recent years, China has implemented several measures to improve air quality. The Beijing-Tianjin-Hebei (BTH) region is one area that has suffered from the most serious air pollution in China and has undergone huge changes in air quality in the past few years. How to scientifically assess these change processes remain the key issue in further improving the air quality over this region in the future. To evaluate the changes in major air pollutant emissions over this region, this paper employs ensemble Kalman filtering (EnKF) for integrating the national ground monitoring pollutant observation data and the Nested Air Quality Prediction Modeling System (NAQPMS) simulation data to inversely estimate the emission rates of SO2, NOX, CO, and primary PM2.5 over BTH region in February from 2014 to 2019. The results show that SO2, NOX, CO, and primary PM2.5 emissions in the BTH region decreased in February from 2014 to 2019 by 83%, 37%, 41%, and 42%, while decreases in Beijing during this period were 86%, 67%, 59%, and 65%, respectively. Compared with the prior emission inventory, the inversion emission inventory reduces the uncertainty of multi-pollutant simulation in the BTH region, with simulated root mean square errors of the monthly average concentrations of SO2, NOX, PM2.5, and CO reduced by 41%, 30%, 31%, and 22%, respectively. The average uncertainties of SO2, NOX, PM2.5, and CO inversion emissions in 2014–19 are ±14.03% yr−1, ±28.91% yr−1, ±126.15% yr−1, and ±43.58% yr−1. Compared with the uncertainty of MEIC emission, the uncertainties of all species changed by +2% yr−1, −2% yr−1, −26% yr−1, and −4% yr−1, respectively. The spatial distribution results illustrate that air pollutant emissions are mainly distributed over the eastern and southern BTH regions. The spatial gap between the inversion emissions and MEIC emissions was further closed in 2019 compared to 2014. The results of this paper can provide a new reference for assessing changes in air pollution emissions over the BTH region in recent years and validating a bottom-up emission inventory. [ABSTRACT FROM AUTHOR]

Background Limited studies have examined the effect of prenatal exposure to particulate matter with diameter of <2.5 µm (PM2.5) and <1 μm (PM1) on fetal growth using ultrasound measurements with inconsistent results. No study has evaluated the joint effect of the indoor air pollution index and ambient particulate matter on fetal growth. Methods We conducted a prospective birth cohort study in Beijing, China in 2018, including 4319 pregnant women. We estimated prenatal PM2.5 and PM1 exposure using a machine-learning method and calculated the indoor air pollution index based on individual interviews. Gender- and gestational age-adjusted Z-score of the abdominal circumference (AC), head circumference (HC), femur length (FL) and estimated fetal weight (EFW) was calculated and then undergrowth was defined. A generalized estimating equation was used to evaluate the individual and joint effect of indoor air pollution index, PM2.5 and PM1 on fetal Z-score and undergrowth parameters. Results One unit increase in the indoor air pollution index was associated with −0.044 (95% CI: −0.087, −0.001) and −0.050 (95% CI: −0.094, −0.006) decrease in the AC and HC Z-scores, respectively. PM1 and PM2.5 were associated with decreased AC, HC, FL and EFW Z-scores, and higher risk of undergrowth. Compared with exposure to lower PM1 (≤ median) and no indoor air pollution, those exposed to higher PM1 (> median) and indoor air pollution had decreased EFW Z-scores (β = −0.152, 95% CI: −0.230, −0.073) and higher risk of EFW undergrowth (RR = 1.651, 95% CI: 1.106, 2.464). Indoor air pollution and ambient PM2.5 exposure had a similar joint effect on the Z-scores and undergrowth parameters of fetal growth. Conclusions This study suggested that indoor air pollution and ambient PM exposure had individual and joint negative effects on fetal growth. [ABSTRACT FROM AUTHOR]

Air pollution and ischemic stroke (IS) are both vital factors affecting the health of Beijing citizens. This study aims at exploring the associations between air pollution, meteorology, and the hospital admission of IS (IS HA). Information on 476,659 IS inpatients in secondary and higher hospitals in Beijing from 2013 to 2018 were collected. A time-stratified case-crossover design with the generalized additive model and the distributed lag nonlinear model were used. In the single-pollutant models, an inter-quartile range increase in O3, SO2, CO, and NO2 resulted in a significant highest increase in IS HA by 2.23% (95% CI: 1.56%, 2.90%), 1.53% (95% CI: 1.12%, 1.95%), 1.05% (95% CI: 0.70%, 1.40%), and 0.51% (95% CI: 0.24%, 0.79%) on the day of pollution, so did PM2.5 and PM10 by 1.13% (95% CI: 0.68%, 1.59%) and 1.19% (95% CI: 0.74%, 1.64%) at a lag of 0–5 days. There was a nonlinear relationship between meteorology and IS HA. In the multivariate model, the cumulative relative risks with a maximum lag time of 21 days of PM2.5 and NO2 were 1.11 (95% CI: 1.04, 1.19) and 0.88 (95% CI: 0.82, 0.94), while the effects of SO2, O3, and meteorology were insignificant. The findings suggested that particulate pollutants could increase the risk of IS, and the elderly were more sensitive to it, while the results of gaseous pollutants are still discordant. The control of air pollution and the protection of susceptible populations should receive higher attention from policymakers. [ABSTRACT FROM AUTHOR]

Air pollutants' effect on ischemic stroke (IS) has been widely reported. But the effect of high-level concentrations during people's outdoor periods among hypertension patients was unknown. Peak-hour concentrations were defined considering air pollutants' high concentrations as well as people's outdoor periods. We conducted a time-series study and used the generalized additive model to analyze peak-hour concentrations' acute effect. A total of 315,499 IS patients comorbid with hypertension were admitted to secondary and above hospitals in Beijing from 2014 to 2018. A 10 µg/m3 (CO: 1 mg/m3) increase of the peak-hour concentrations was positively associated with IS hospital admissions among hypertension patients. The maximum effect sizes were as follows: for PM2.5, 0.17% (95% confidence interval [CI]: 0.10–0.24%) at Lag0 and 0.22% (95% CI: 0.12–0.33%) at Lag0–5; for PM10, 0.09% (95% CI: 0.05–0.13%) at Lag5 and 0.17% (95% CI: 0.09–0.26%) at Lag0–5; for SO2, 0.87% (95% CI: 0.46–1.29%) at Lag5; for NO2, 0.83% (95% CI: 0.62–1.04%) at Lag0 and 0.86% (95% CI: 0.59–1.13%) at Lag0–1; for CO 1.23% (95% CI: 0.66–1.80%) at Lag0 and 1.33% (95% CI: 0.33–2.35%) at Lag0–5; for O3 0.23% (95% CI: 0.12–0.35%) at Lag0 and 0.20% (95% CI: 0.05–0.34%) at Lag0–1. The effect sizes of PM2.5, NO2, and O3 remained significant after adjusting daily mean. Larger effect sizes were observed for PM2.5 and PM10 in cool season and for O3 in warm season. As significant exposure indicators of air pollution, peak-hour concentrations exposure increased the risk of IS hospital admissions among hypertension patients and it is worthy of consideration in relative environmental standard. It is suggested for hypertension patients to avoid outdoor activity during peak hours. More relevant searches are required to further illustrate air pollutant's effect on chronic disease population. [ABSTRACT FROM AUTHOR]

The Chinese environment is experiencing the "U-Type" course from sharp deterioration to significant improvement. In order to achieve the fundamental improvement of the ecological environment, China has implemented several relevant policies and strategies. Among them, the development of urban rail transit, as an essential measure to improve the ecological environment in China, has attracted more and more attention, but the research on the interactive coercion relationship between rail transit and the ecological environment is minimal. Therefore, this study selected ten cities opening urban rail transit before 2005 in mainland China as research objects and established an urban rail transit and ecological environment comprehensive evaluation index system. Then, the interactive coercing model and coupling coordination model were used, and the dynamic relationship between urban rail transit and the ecological environment was explored. The research results in this study showed that (1) there is an apparent interactive coercion relationship between urban rail transit and the ecological environment, and the evolution trajectory conforms to a double exponential curve. (2) From 2006 to 2019, Wuhan's ecological environment pressure index showed a continuous downward trend. The ecological environment improved the fastest. The rest of the cities showed a trend of first rising and then falling. (3) The type of coupling coordination degree of urban rail transit and ecological environment showed a changing coordination trend from severe incoordination—slight to incoordination—basic to coordination—good. Beijing has the highest degree of overall coordinated development in urban rail transit and the ecological environment. The results of this study can provide a theoretical reference for the realisation of the virtuous circle development of rail transit and the ecological environment. [ABSTRACT FROM AUTHOR]

Background: Few studies have considered the interplay between commuting mode and air pollution on obesity. The aim of this study was to examine whether workplace air pollutants exposure modifying the associations between different commuting mode and obesity. Methods: A cross-sectional study of workers in Beijing was conducted in 2016. The study sample comprised 10,524 participants aged 18 to 65 years old. Outcomes were defined as overall obesity (BMI≥ 28 kg/m2) and abdominal obesity (WC ≥ 85 cm in men and WC ≥ 80 cm in women). Commuting modes were divided into walking, cycling, bus, subway, and car or taxi. Logistic regression models were used to estimate odds ratios relating commuting mode to overall and abdominal obesity and stratified by gender, controlling for covariates. Results: The association between commuting mode and obesity was more strongly in men than women. In the fully adjusted models, compared with car or taxi commuters, cycling (men: OR=0.37, 95% CI=0.20 to 0.68) or bus (men: OR=0.58, 95% CI=0.36 to 0.94) counterparts had a lower risk of overall obesity. Compared with car or taxi commuters, walking (men: OR=0.57, 95% CI=0.36 to 0.91), bus (men: OR=0.59, 95% CI=0.39 to 0.89), or subway (men: OR=0.59, 95% CI=0.39 to 0.89) counterparts had a lower risk of abdominal obesity. We observed significant interactions between exposure PM10 and cycling on overall obesity in men. After adjusting for air pollutants, the association between commuting mode and obesity was slightly strengthened. Conclusion: This study findings indicate that active (walking or cycling) or public (bus or subway) commuting modes were protected factors for overall and abdominal obesity among men. Air pollutants do not obscure the benefits of active or public commuting for obesity. These associations support the policy for increasing active or public commuting as a strategy to reduce the prevalence of obesity. [ABSTRACT FROM AUTHOR]

Diabetes mellitus (DM) is a common chronic disease worldwide. Ambient air pollution has long been proven to be associated with type 2 diabetes mellitus (T2DM) progression, but the underlying mechanism is not clear yet. In addition, previous studies mainly focused on the prevention of healthy people against the incidence of T2DM. We designed a panel study including two follow-ups and enrolled 39 patients with T2DM living in Beijing. Linear mixed model was fitted to assess the association between two pairs of variables (ambient air pollution exposure and C3 levels, ambient air pollution exposures and T2DM index). Mediation analysis of C3 between ambient air pollution exposure and indicators of T2DM progression was conducted. We found that PM2.5 exposures is are negatively associated with serum complement C3. Given that C3 might act as a protector of pancreas β cell, PM2.5 exposures could accelerate disease in T2DM populations. No mediation effects were found. This study reveals that exposures to PM2.5 can cause progression of diseases among T2DM populations. [ABSTRACT FROM AUTHOR]

Radical measures for controlling ambient air pollution sources were employed by the Chinese government during the Asia-Pacific Economic Cooperation (APEC) meeting in 2014, providing a unique case to evaluate the health effect benefits from such measures. To examine the cancer risk reduction from the source control measures during the APEC meeting, we estimated the reduction in population exposure to PM 2.5 and PAHs and the reduction in PAHs-associated cancer risk if the control measures were sustained over time. We determined the population exposure to PM 2.5 and PM 2.5 -bound PAHs for the 21.52 million Beijing residents using a Land Use Regression model to determine the spatial distribution of PM 2.5 and a Monte Carlo approach to revise indoor/outdoor infiltration factor and time activity patterns. Into the model and approach, we incorporated the spatial variance and indoor/outdoor differences in the PM 2.5 and PM 2.5 -bound PAHs concentrations, based on measurements. We then estimated lung cancer risk using the population attributable fraction (PAF), assuming the control measures were sustained over time. The mean PM 2.5 exposure concentration decreased from 37.5 μg/m3 (CI:17.1–74.9 μg/m3) to 24.0 μg/m3 (CI:10.2–47.7 μg/m3), whereas the mean PM 2.5 -bound equivalent benzo[ a ]pyrene (BaP eq ) exposure concentration decreased from 7.1 ng/m 3 (CI:3.3–14.2 ng/m 3 ) to 4.2 ng/m 3 (CI:1.8–7.7 ng/m 3 ), resulting in a reduction in the lung cancer PAF from 0.75% to 0.45%, if the measures were sustained over time. [ABSTRACT FROM AUTHOR]

Abstract: North China is known for its large population densities and rapid development of industry and agriculture. Air quality around Beijing improved substantially during the 2008 Summer Olympics. We measured atmospheric concentrations of various Nr compounds at three urban sites and three rural sites in North China from 2010 to 2012 and estimated N dry and wet deposition by inferential models and the rain gauge method to determine current air conditions with respect to reactive nitrogen (Nr) compounds and nitrogen (N) deposition in Beijing and the surrounding area. NH3, NO2, and HNO3 and particulate NH4 + and NO3 −, and NH4 +–N and NO3 −–N in precipitation averaged 8.2, 11.5, 1.6, 8.2 and 4.6 μg N m−3, and 2.9 and 1.9 mg N L−1, respectively, with large seasonal and spatial variability. Atmospheric Nr (especially oxidized N) concentrations were highest at urban sites. Dry deposition of Nr ranged from 35.2 to 60.0 kg N ha−1 yr−1, with wet deposition of Nr of 16.3 to 43.2 kg N ha−1 yr−1 and total deposition of 54.4–103.2 kg N ha−1 yr−1. The rates of Nr dry and wet deposition were 36.4 and 33.2% higher, respectively, at the urban sites than at the rural sites. These high levels reflect the occurrence of a wide range of Nr pollution in North China and suggest that further strict air pollution control measures are required. [Copyright &y& Elsevier]

Surface soil samples were collected from 52 sites around Guanting Reservoir in Beijing, China, and contents of ‘total’ metals (Cu, Zn, Pb, Cd, As, Ni and Cr) were determined. The results indicate that the degree of heavy metal pollution in the soils declines in the order of Cd>Cr>Zn>As>Cu>Ni>Pb. Based on the results of a combination of multivariate statistics and geostatiscal analyses, it was concluded that land application of phosphate fertilizer, wastewater and sludge were the primary sources of Cd and Zn in soils. Whereas As, Cu, Cr and Ni in some soils were due to natural rock weathering. The sources of Pb in soils only partially originated from land application of phosphate fertilizer, but mainly from vehicle exhaust. The greatest concentrations of all metals, except for Pb, were found in Huailai County and the towns of Yanghedaqiao and Guanting. [Copyright &y& Elsevier]

PM2.5 level has decreased significantly in Beijing in recent years due to the strict air quality control measures taken in Jingjinji Region and the surrounding areas. However, the variation characteristics of the concentrations of PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) in Beijing in recent years are still not so clear. In order to understand the pollution status of PM2.5-bound PAHs in Beijing, fifteen PAHs were measured in a typical urban area of Beijing from 1 March to 20 March 2018. The average mass concentration of the 15 PAHs was 21 ng/m3 and higher in the nighttime than that in the daytime. The proportion of 4-ring PAHs in 15 PAHs was highest (43%), while 6-ring PAHs was lowest (10%). The levels of PAHs were higher during heavy pollution episodes than those in non-heavy pollution episodes, and the proportions of 5- and 6-ring PAHs were increased during a heavy pollution episode. PAHs posed obvious carcinogenic risks to the exposed populations, and the risk was higher during heavy pollution episodes than the average value of the whole monitoring period. The main sources of PAHs were traffic emissions and coal/biomass burning. Air masses from the south-southeast had a great influence on the PM2.5 levels during a heavy pollution episode. It is recommended that not only the PM2.5 levels but also the PAHs levels bounded in PM2.5 should be controlled to protect human health in Beijing. [ABSTRACT FROM AUTHOR]

While the economy and society of China are developing rapidly, various ecological and environmental problems continue to emerge. The problem of air pollution is becoming an issue of increasing concern. Since 2013, Beijing, Tianjin, and Hebei Provinces have collaborated to control air pollution and have achieved certain success. However, the air pollution problem in the capital, Beijing, remains severe. In this study, a quantitative evaluation and analysis method is established for assessing urban air quality and its influencing factors by developing a driving force model. The model combines multiple regression and principal component analysis to account for social, economic, meteorological, and regional factors. The influencing factors with the highest contributions are regional transmission, energy consumption, and industrial structure. This model is used to project the future trend of the air quality in Beijing based on the evolution of the influencing factors, aimed to provide a theoretical basis for policies improving Beijing's air quality. • A driving force model of the air quality in Beijing is established. • Factors influencing the annual air quality and their contributions are determined. • Future trends in air quality in different scenarios are explored. • Practical policy implications are proposed based on factor and trend analyses. [ABSTRACT FROM AUTHOR]

China has experienced extreme urban heat island effects and air pollution associated with rapid urbanization. Optimizing urban ventilation environment could relieve these environmental problems. In this study, an Urban Ventilation Network Model (UVNM) was developed to explore the impact of urban morphology and building height on the urban ventilation condition. The study calculated the ventilation resistance coefficient of building height according to fluid mechanics, and then determined the least cost path among the air inlets and outlets considering the direction and frequency of wind. Eventually, corridors at several different levels of ventilation were extracted by classifying the line densities of least cost paths, which were effectively verified through land surface temperature retrieved from the Landsat Thematic Mapper. The new model is more scientific and convenient than traditional urban construction environmental assessment software in terms of data acquisition and hardware support. The results suggest that urban design based on urban morphology and building height and considering the direction and frequency of wind would be effective for optimizing ventilation to regulate urban environmental problems. [ABSTRACT FROM AUTHOR]

Beijing suffered from serious air pollution in October, 2011 with the occurrence of three continuous episodes. Here we analyze the pollution status of particulate matter, the relationship between the gaseous pollutants, physical and chemical properties of single particles, and the profile of water-soluble ions in PM 2.5 during the three episodes. Regional and photochemically aged air masses, which were characterized as having high values of O 3 and SO 2 , were hypothesized to have played a dominant role in the first episode. After mixing local air masses with freshly-emitted primary pollutants, the concentration of NO x continued to increase and the size of SO 4 2– NO 3 − and NH 4 + in the particle population continued to become smaller. The amount of elemental carbon-rich and organic carbon-rich particles in the scaled single particles (0.2–2 μm) and water-soluble K + in PM 2.5 also increased in the episodes. All the available information suggests that the biomass or fuel burning sources in or around Beijing may have had a huge impact on the last two episodes. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the lag effects and seasonal differences of urban air quality change on human health, we carried out a time-series analysis of daily general practitioner consultations for allergic rhinitis (AR) in Beijing, China. In earlier publications we had assessed the relative risks of air pollutants on AR in Beijing during the period 2009–2010. This article analyzes for the same time period the lag effects of air pollutants and the seasonal effects on daily number of outpatient with allergic rhinitis; differences among age groups and gender groups were also taken into consideration. The results show that, the largest effect RRs of PM10 were at lag01, lag0, lag01, lag01, and lag01 for the total population, male, female, young/middle aged people (20–60years age group), and old people (more than 60years age group), respectively. The largest associations of SO2 were observed at lag3, lag1, lag3, lag0 and lag0 for the total population, male, female, young people/middle aged people (20–60years age group), and old people (more than 60years age group), respectively. The strongest effects of NO2 were found at lag03 for the total population, female and the young/middle aged people; at lag0 for male and lag03 for elder people. RRs of the three pollutants for AR have shown a decreasing relevance from NO2 to PM10 to SO2. The seasonal effect models show that PM10, SO2, and NO2 had higher risk for AR in the warm season than in the cold season. [Copyright &y& Elsevier]

Exposure to ambient particulate matter with a diameter of <2.5 μm (PM 2.5) has been linked to increases in blood pressure. The aim of this study was to assess the effects of short-term exposure to PM 2.5 on blood pressure in office workers in Beijing, China. A total of 4801 individuals aged 18–60 years underwent an annual medical examination between 2013 and 2017. Levels of air pollutants were obtained from 35 fixed monitoring stations and correlated with the employment location of each participant to predict personal exposure via kriging interpolation. Linear mixed-effects models were used to estimate the changes in blood pressure associated with PM 2.5 exposure at various lag times. After adjusting for personal characteristics and other potential confounders, each interquartile range increase in PM 2.5 was associated with a 0.413-mmHg (95% confidence interval [CI]: 0.252–0.573), 0.171-mmHg (95% CI: 0.053–0.288), 0.278-mmHg (95% CI: 0.152–0.404), and 0.241-mmHg (95% CI: 0.120–0.362) increase in systolic blood pressure, diastolic blood pressure, pulse pressure, and mean arterial pressure, respectively (p < 0.05). Men, individuals previously diagnosed with hypertension, and subjects working in the northern districts of Beijing had larger changes in blood pressure, and the effect sizes were 0.477-mmHg (95% CI: 0.286–0.669), 0.851-mmHg (95% CI: 0.306–1.397, and 0.672-mmHg (95% CI: 0.405–0.940). The findings suggested that exposure to PM 2.5 had adverse effects on blood pressure, especially among males and hypertensive patients. Image 1 • Individual PM 2.5 exposure was measured by Kriging interpolation method. • Blood pressure increased significantly with elevations in PM 2.5 for lag 4–6 days. • Stronger effects were found among males and hypertensive patients. [ABSTRACT FROM AUTHOR]

Secondary aerosol (SA) is considered to be an increasingly dangerous air pollutant. However, quantification of SA has suffered from considerable uncertainty due to its poorly understood formation mechanism. In this study, a simplified approach based on characterizing coal combustion emission indicators polonium-210 (210Po), selenium (Se) and arsenic (As) was used to estimate SA loading (increment) during a heavy air pollution event in December 2016 in Beijing. Due to the insignificant input and output of air pollutants as well as the assumption of non-local emissions during this heavy air pollution event, a steady-state method of severe air pollution has been proposed to estimate SA increment (the sum of newly formed secondary inorganic aerosols and secondary organic aerosols) during this typical air pollution event. Corresponding algorithm of the method was developed depending on the characteristics of coal combustion related pollutants (210Po, Se, and As). The results indicated that the median contribution of newly formed SA to total suspended particulates (TSP) during this heavy air pollution event was 42.4% (interquartile range [IQR]: 36.6%–48.8%), which quantitatively confirms the dominant contribution of substantial enhancement of SA to heavy air pollution. Although further verification is needed, this steady-state method of evaluating severe air pollution has potential for quantification of the SA increment. Image 1 • 210Po, Se, and As can be used to estimate the SA increment in heavy pollution events. • 210Po activity concentration reached a plateau once the TSP concentration exceeded ~300 μg m−3. • The stagnant accumulated closed box model was proposed to quantify the SA increment. • The input and output of 210Po was negligible during stagnant accumulated heavy air pollution. • The explosive growth of SA was the dominant contributor to heavy air pollution. [ABSTRACT FROM AUTHOR]

Previous studies have mainly focused on the associations between particulate matters and infant mortality. However, evidence regarding the associations between gaseous pollutants and mortality among children aged <5 years remains sparse. The aim of this study was to investigate the associations between ambient air pollution and death among children aged <5 years in Beijing, China, and explore the impact of age, gender and specific causes of death on these associations. Concentrations of ambient air pollution and the number of deaths among children aged <5 years in Beijing from January 2014 to September 2016 were extracted from authoritative electronic databases. The associations were estimated for a single-month lag from the current month up to the previous 5 months (lag0-lag5) and moving averages of the current and previous months (lag01-lag05) using generalized additive Poisson regression (adjusted for time trends, season, meteorological variables and holidays). Subgroup analyses related to age, gender and specific diseases were performed. Two-pollutant models were used to evaluate the possible role of single pollutants. Sulfur dioxide (SO 2), nitrogen dioxide (NO 2) and carbon monoxide (CO) demonstrated the strongest associations with death among children aged <5 years at lag0, and the estimates decreased or even turned negative with the increasing lag periods. For an interquartile range increase in SO 2 , NO 2 and CO at lag0, the odds ratios (OR) were 1.332 (95% CI 1.152-1.539), 1.383 (95% CI 1.113-1.718) and 1.273 (95% CI 1.028-1.575). However, CO lost significance after adjusting for SO 2 and NO 2 , and PM 2.5 gained significance (OR 1.548, 95% CI 1.061-2.258) after adjusting for PM 10. The ORs for SO 2 and NO 2 remained the most stable across all two-pollutant models. The associations for children aged 1–5 years were stronger than those reported for infants at lag0 but lower at the other lag months. The pollutant associations were stronger for congenital heart disease-related death than overall and pneumonia-related death. We did not find significant differences in terms of gender. Exposure to air pollution may increase the incidence of death among children aged <5 years. SO 2 and NO 2 may be the most stable pollutants reflecting associations between air pollution and death, deserving further attention. Children with congenital heart diseases are more susceptible to air pollution. Therefore, it is urgent to implement the clean air targets established by WHO and reduce the exposure of children to air pollution. • Exposure to ambient air pollution may account for increased deaths among children aged <5 years in Beijing, China. • SO 2 and NO 2 may be the most stable pollutants reflecting the associations of death, deserving further attention. • Children with congenital heart diseases are more susceptible to air pollution. [ABSTRACT FROM AUTHOR]